There are known signal generators including an analogue comparator CA to which is connected a triangular signal Vi and a continuous input signal Ve whose amplitude is a reference voltage as seen in FIG. 1. During operation of comparator CA, the input signal and the triangular signal are compared to deliver an output signal. The output signal takes the form of a rectangular signal. Indeed, the output signal Vs is a continuous signal which switches when the triangular signal voltage attains the input signal voltage value. Consequently, the output signal has a regular square shape. This square signal then has a pulse width, i.e. a ratio between the high state or low state of the signal and the period. This ratio corresponds, in the case of the arrangement described, to the ratio between the reference voltage and the triangular signal amplitude.
One drawback of this arrangement is that it requires the comparator CA to be fast, since the latter has to switch at each time interval and the switching has to be fast to avoid affecting the output signal.
Further, the duty cycle α is adjusted by modifying the reference voltage value. The triangular signal amplitude must be linked to the reference signal voltage value. If this is not the case, an error occurs in the duty cycle and the latter is not the desired ratio.
It is also known to use a clock having a frequency N times higher than the desired output signal frequency. This ratio of N is the discrete number of steps of the duty cycle change. To achieve this, a high frequency synchronous counter and a digital comparator at the counter output are commonly used. The desired duty cycle is the comparison value of the comparator.
However, this technique is high power consuming, particularly if the frequency increases and if the resolution, i.e. the number of steps, increases.